we are working on a 78 302 and need to know what to set the timing @...some people i talked to say 8 to 10 but their not to sure,,and is their any way to check the total timing, also the carb is a 2brle (holly) 500 cfm .the only place i see to put the vacume advance is in a tube on the side of the meetering block,but when i hooked the vacume gauge to it,,it did'nt pull any vacume...will this change when the truck is under load??

 

Moved to proper forum. I will let the experts here explain ported vacuum.

 

You wanna hook the vacuum advance to a port that has zero vacuum at idle. So you probably had the right port. I believe most carb models call for 6BTDC on the stock timing, but going with 8-10 BTDC won't hurt anything, as long as there is no preignition or detonation. Good luck

 

you can check total timing with a advance light or mark about 30 degrees on the damper and rev up the motor some and see how far it goes past it. You should have more then 30 but you can get a good ideal. 36 to 40 degrees of total timing is about the most you can run safely. for inital I'd run 12 btdc cause it gets more power and better fuel econmy but stock is about 6 to 10 degrees.

 

put a vacuum gauge on the intake manifold vacuum tree and adv. the dist to the highest vacuum reading back the timing off until the gauge drops one inch and set the dist at that point and you'll have optimum adv. forget the timing light as each motor is a individual when it comes to initial adv. and the vacuum method never seems to fail.